This is William Smith’s original geological map of the British Isles, first unveiled in 1815 . On aesthetic grounds alone it might qualify as a great work of art, for it is a thing of true beauty. But its true greatness lies in what it represents: an entirely new way of thinking about the ground beneath our feet.
Anyone who travels away from their hometown will observe that every region has its own unique geography, but not so many realise how intimately these differences are connected to changes in the character of the rocks that the landscape is built upon; that the contrast between the low rolling hills of south east England, and the hardy crags of Scotland, is largely due to the difference between soft chalk and ancient baked granites that form their respective foundations. Fewer still realise that these changes have an underlying order to them. Distinct packages of different rocks, with their own unique and consistent composition and fossil content, can be traced across large distances; and their arrangement, whilst sometimes complicated, is far from haphazard.
William Smith realised all of these things, and his map spectacularly revealed something entirely new within the familiar outline of the British Isles: a pattern to British geology that none had fully grasped before. By demonstrating that there was such a pattern, and that it was possible to systematically unravel it, he put us firmly on the path to understanding the processes that might have produced it.
(if you want the more modern version of this map…)